A thermotherapy device with a reclining surface and with a radiant heating means is known from DE 20 2006 017 424 U1. An infrared lamp is provided as a radiant heater and a control means is used to control the radiant energy radiated by the radiant heater. The distance between the heating means and a test subject, who is located on the reclining surface, is detected by means of a distance-measuring means. The control means is designed such that a preselected radiation density becomes established on a reference surface, which is preferably arranged at or near the object, at a given distance from the test subject. The radiation output of the radiant heater is changed on the basis of the distance signal of the distance-measuring means such that the preselected radiation density on the reference surface remains essentially constant.
The drawback of the prior-art device is that the detection of the position of the test subject being irradiated in relation to the radiant heater by means of distance sensors is relatively complicated, because individual measured distance values are determined at first, and the angular offset of the reclining surface in relation to the radiant heater is then determined by linking individual measured values by means of a calculation formula. If the distance measurement is disturbed, because, for example, medical treatment procedures are carried out at the test subject, breathing tubes are displaced or brought inadvertently into the area detected by the distance-measuring means, incorrect setting may result at the radiant heater and a nonuniform radiation density becomes established.